Mechanical underfeed stoker



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Patented July 19, 1932 UNITED STATES PATENT oFFlCE VERNON G. Lusen, or CHICAGO, ILLINOIS, AssIGNon. 'ro MODERN coAL BURNER, com' PANY, or omesso, ILLINOIS, A conroRA'rIoN or ILLINOIS MECHANICALA UNDERFED STOKER Application mea August 24, 1929. serial No. 388,064.

This invention relates to a mechanical underfeed Stoker and more particularly to means including a screw conveyor for feeding coal and the like to a retort of a mechanical underfeed stoker and there distributing the coal.Y

The present invention constitutes an 1mprovement on my invention disclosed in an application entitled Material feeder, Serial No. 229,056, filed October 27, 1927. A It is an object of the present invention to provide means for feeding fuel to the retort of an underfeed Stoker with a minimum consumption of power and minimum tendency for the fuel to become clogged or rammed while it is being fed into the retort.

It is a. further important object of this invention to provide a screw conveyor for mechanical underfeed fstokers of such construction that fuel can be fed by said conveyor into the retort of the Stoker without jamming and packing and can be equally distributed in Said retort or the distribution of said fuel varied to suit conditions.

Other and further important objects of this invention will become apparent from the following description and the accompanying drawings.4

This invention (in a preferred form) is illustrated in the drawings and hereinafter more fully described.

On the drawings:

Figure 1 is a transverse sectionall view through a mechanical underfeed stoker of my invention.

Figure 2 is a longitudinal elevational view of the mechanical underfeed Stoker.

lFigure 3 is a top plan view of the same, and

Figure 4 is an -elevational view of the screw conveyor. 4

Figure 5 is an enlarged sectional view taken on line V-V of Figure 4.

As shown on the drawings: The reference numeral 1 indicates a furnace wall comprising a lower wall of masondicated as a whole by the reference numeral 4, of my invention. Said mechanical Stoker 4 comprises a hopper 5 and a retort 6 joined thereto by means of a sectional conduit 7. Tuyre blocks l8 aire mounted along the upper edges of the side walls of said retort 4 and partially supported thereby and by angle irons 9. Dead plates 10 are'positioned between said tuyre blocks 8 and the walls of said housing 1, being Supported in part upon the masonry walls 2. Front and rear plow plates 11 and 12v are mounted at the respective ends of said retort 6. f f i A screw conveyor indicated as a whole by the reference numeral 13 extends from the 7 the full length of said retort bottom 6.

Said screw conveyor 13 comprises a plurality of helical -vanes cast in separate sections, as for` instance the sections 14 to 19 inclusive, and mounted upon a squarev shaft. 20. Said shaft`2() is provided at its front end with a collar 21 journalled in a thrust bearing 22 and at its rear end in asimple Sleeve bearing` 23 mounted in the rear wall of said retort 6. Said thrust bearingy 22 is adapted to be supplied with a lubricant by means of a pipe connection 24.

Means for driving the screw conveyor 13 may suitably comprise a motor 25 and a reducing mechanism 26 gear connected to the squarewshaft 20 of said` screw conveyor 13.

Inasmuch as the collar 21 is slidably mounted upon the square shaft 20, there is no thrust upon said shaft but all of the thrust is taken up in the thrust bearing 22.

In order to prevent 4packing and jamming of the fuel, the flights of the screw conveyor 13 are made of varying pitch and diameter. For instance, in the section 14 in the bottom of the hopper 5, the helical {iights are of constant pitch but of increasing diameters as they approach the conduit 7 and the sections 15 and 16 within said conduit 7 have flights of substantially the same diameter as the inside diameter of Said conduit with a pitch greater than that of the flights on section 14.

At approximatelyY the junction between the conduit 7 and the retort 6, a'portion'of the flights is removed to provide a gap 27, the end 28 of the helical flights serving as a propeller to push the fuel across said gap to be again taken up by the flights on the section 17. The purpose of providing the gap 27 is to prevent excessive jamming and packing of the fuel at the point at which it is fed into the retort to the smaller pitch screw. The removal of a segment or segments of the flight has the same effect as a local reduction in the diameter of the screw.

In a similar manner, smaller `gaps 29 and 30 are provided for a fraction of the turn of the flights on the sections 17 and 18 so as to enable the screw conveyor to effectively distribute the fuel Within the retort 6. Practically, it is sullicient to knock off portions of Athe flight at opposite sides thereof, as at 4() and 41 (Figure 5) to provide propeller-like blades 42 and 43.

If after the Stoker is installed, the fuel bed is found to be improperly formed, a low spot in the fuel bed may be built up by making a propeller in that portion of the distributing screw which affects the low area of the fuel bed. A propeller locally reduces the carrying capacity of the distributing screw and gives substantially the same effect as reducing its diameter at that point. Also, it offers a quick and inexpensive method of controlling the amount of fuel rejected from any portion o-f the distributing screw.

Experience has indicated that it is imposl sible to calculate for all types of fuel the proper pitch and diameter for the flights on a screw conveyor of this type for each portion of the length of said conveyor. It has been found, however, that by removing a portion of the helical flights at certain points along the length of the screw conveyor, very satisfactory distribution of the fuel in the retort can be obtained without the necessity of providing specially constructed screw conveyors for every condition of fuel feeding that may obtain due to different types of fuels used.

In addition to the provision of gaps along the length of the screw conveyor to provide propeller-like action on the part of the ends of the flights so formed, it has also been found preferable to provide a deflector member, indicated as a whole by the reference numeral 31.- Said deflector member 31 is adjustably positioned'along one wall of the retort 6 adjacent'the side of the screwconveyor 13 having an upward movement. member 31 may suitably comprise an angle iron '32 having slotted legs 33 for adjustable mounting upon pins 34. The angle iron .32 may thus be adjusted vertically to suit the particular requirement and when in the correct position will cause an equal distribution of the fuel to either side of the fuel bed retort. Without a deflector member 31, it has been found that the fuelin general builds up more on one side of thefuel bed than the other.

It is to be understood that the gaps 29, .I

and 30 in .the flights of the screw conveyor 13v need not necessarily be positioned at any particular point or points along the length of said conveyor but the positioning of these gaps will to some extent depend upon the conditions under which the mechanical underfeed stoker is operating, the nature of the fuel and like variables. In conjunction with the construction of flights of varying pitch and diameter, the provision of these gaps, whereby the flights act at points along the length of the conveyor as propellers, insures an even and satisfactory distribution of the fuel in the fuel bed. i

I am aware that many changes may be made and numerous details of construction maybe varied through a wide range without departing from the principles of this invention, and I, therefore, do not purpose limiting' the patentgranted hereon otherwise than necessitated by the prior art.

I claim as my invention:

In an underfeed stoker including a hopper, a retort casing, and a conduit connecting said hopper and said retort casing, a screw conveycr having a. plurality of helical flights, said conveyer having a portion thereof extending in the retort casing, said portion of` the conveyor being substantially continuous and having segmental portions of certain flights thereof entirely cut away on opposite sides of the longitudinal axis of the conveyer to provide propeller-like blades.

In testimony whereof I have hereunto subscribed my name at Chicago, Cook County,

Illinois.

VERNON G. LEACH.

Said deflector los 

